package bishi;

import java.util.Scanner;

/**
 * @Author liuhaoqi
 * @Date 2020/8/24 22:18
 * @Version 1.0
 */
public class Huiding02 {
        public static void main(String args[]) throws Exception {
            Scanner cin = new Scanner(System.in);
            int n = cin.nextInt();
            System.out.println(f(n));
        }

    public static int f(int n) {
        if (n <= 2) {
            return 1;
        } else {
            return f(n - 1) + f(n-2);
        }
    }

}
